Why the dash in foo-baz is not replaced?

1)The s/-/_/g command operates line by line before all lines are appended by N.

2)The second line (foo-baz) has dash not replaced yet while being appended.

3)The replacement command does not rerun on the combined, newline-removed string.

Result: the dash remains in the final joined output.

Why the dash in foo-baz is not replaced?

1. The s/-/_/g command operates line by line before all lines are appended by N.

2. The second line (foo-baz) has dash not replaced yet while being appended.

3. The replacement command does not rerun on the combined, newline-removed string.

Result: the dash remains in the final joined output.